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[Studies in Computational Intelligence 481] Artur Babiarz, Robert Bieda, Karol Jędrasiak, Aleksander Nawrat (auth.), Aleksander Nawrat, Zygmunt Kuś (eds.) - Vision Based Systemsfor UAV Applications (2013, Sprin

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262 H. Josiński et al.<br />

Table 6. Two class problems, experiment 2<br />

TP TN FP FN Precision Sensitivity Sensibility<br />

FYC 10 30 0 0 100% 100% 100%<br />

HY 9 29 1 1 95% 97% 90%<br />

LJG 9 29 1 1 95% 97% 90%<br />

LQF 10 30 0 0 100% 100% 100%<br />

4 Multil<strong>in</strong>ear Pr<strong>in</strong>cipal Component Analysis<br />

Multil<strong>in</strong>ear pr<strong>in</strong>cipal component analysis, proposed <strong>in</strong> [16] is the multil<strong>in</strong>ear extension<br />

of classical PCA method. The <strong>in</strong>put and output data are considered to be<br />

tensor objects and contrary to PCA dimensionality reduction operates directly on<br />

tensors rather than its vectorized form.<br />

A tensor is a multidimensional object, whose elements are addressed by <strong>in</strong>dices.<br />

The number of <strong>in</strong>dices determ<strong>in</strong>es the order of the tensor, where each <strong>in</strong>dex<br />

def<strong>in</strong>es one of the tensor modes [16]. In MPCA an elementary matrix algebra is<br />

extended by two operations: tensor unfold<strong>in</strong>g and the product of a tensor and<br />

matrix. The unfold<strong>in</strong>g transforms a tensor <strong>in</strong>to a matrix accord<strong>in</strong>g to a specified<br />

mode. The tensor is decomposed <strong>in</strong>to column vectors, taken from the perspective<br />

of a specified mode, see Fig. 3.<br />

The tensor X multiplication by the matrix U accord<strong>in</strong>g to mode n is<br />

obta<strong>in</strong>ed by the product of the unfolded tensor and the matrix U. To go back to a<br />

tensor space, an <strong>in</strong>verse unfold<strong>in</strong>g operation is applied. In other words, the mode<br />

n of the tensor X is projected <strong>in</strong>to the matrix U.<br />

Fig. 3. 1,2 and 3-mode tensor matrix product

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